Everything You Need to Know About an Off-Grid Septic System

by Oliver Guess | LAST UPDATED October 13, 2021

two people digging a hole
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If you live in an off-grid tiny house, then that means you’re disconnected from city power lines and water pipes. The power lines aren’t that much of a problem since you can simply use solar panels and run your devices on solar power, but the water pipes could pose a much bigger issue.

If you have a well on your property or a creek near your home, you can manually fill a few large bottles each day and simply use that as drinking water, for cooking, and for any other tasks you might need when living off the grid.

Unfortunately, this method means that your off-grid water supply can cover your basic everyday needs, but it won’t be enough for you to use any washing machines or flush toilets, which brings us to the topic of our article.

Available Options

A tiny home that isn’t connected to any sewage lines obviously can’t rely on a standard flush toilet, so that means that you’ll have to get creative with your waste management.

One of the easiest solutions is to simply dig a hole for your outhouse. After the hole is sufficiently filled up, simply fill in the hole, dig another one, and place your outhouse over the new hole in the ground. Keep in mind that this solution only works if your property is far away from any other house. Otherwise, the neighbors might report you for assaulting their noses with your primitive DIY septic system.

The other method of going off-grid with your toilet needs is to use a portable toilet simply. This can either mean getting something like the Nature’s Head composting toilet, which has a separate tank for both solids and liquids, or something simple like the Reliance Luggable Loo, which is essentially a toilet seat on top of a bucket full of sawdust.

While these toilets take up very little space and don’t require a full DIY septic system to work, you’ll need to manually clean them and dispose of the waste by throwing them in containers that are specifically designed for them.

The final toilet option for your off-grid home is to install a full-on septic system. This is by far the most difficult off-grid waste disposal unit to set up and costs quite a bit more money than simply buying a porta-potty.

However, the long-term convenience of this method makes it the only viable option for anyone looking to maintain this lifestyle for as long as possible, and it really isn’t all that hard to install as long as you know how to do it.

Permits

Even though you’re building your off-grid septic system on your property, you still need to submit the proper documentation to your local government and apply for all of the necessary permits. 

While certain states have different requirements, you’ll usually be required to present certain documents about property ownership, soil samples taken from the property, and an entire plan for the septic system that you’re planning to build.

This means that you need to contact a local construction agency and hire them to draw up the plans based on your requirements. Some people try to do this by themselves, but even trained engineers sometimes have trouble navigating all of the paperwork and procedures necessary to submit these sorts of plans. Therefore, it’s just a waste of time to try and do this on your own.

After the plans have been drawn up, the next move is to set up a meeting with the city planning inspector. This person will, entirely. You look over your plans, ask yourself a few questions, and decide whether to give you a permit or if your designs have flaws that need to be worked out before proceeding.

After a permit has been issued, all that’s left is to start ordering the materials and start digging those holes in your backyard.

Different Tanks

Before we get into the building process itself, the one thing that you need to know is the difference between greywater and blackwater.

Greywater is the runoff that comes from your sinks and items like washing machines, and it’s essentially the leftover water that you don’t drink or use and ends up in the drain.

Blackwater is all of the human waste that you flush down your toilet, which means that it includes both liquids and solids.

For filtration and sanitation reasons, both greywater and blackwater have their tanks that they’re sorted into. This allows you to attach a treatment system directly onto the blackwater tank, which requires a lot more attention when it comes to breaking down the contents and making sure that there are no hazardous spills.

On the other hand, most greywater systems come with the option to reuse the water gathered there. While this wastewater contains too many microorganisms to be safely used to water your vegetable garden, you could still use it to water any plants that aren’t edible.

Collecting Water

If you aren’t connected to a municipal water system, you need to collect water for your toilets differently. We previously mentioned using wells or creeks to gather water, but that’s time-consuming and requires a lot of manual labor to fill up your water tank completely.

The easiest way to increase your water supply is to start collecting rainwater. This process is quite simple and all you really need to do is put a rain gutter around your roof and have at least two drains on either side of the house, which filter into two large water barrels.

The amount of rain you get will depend on your local weather conditions, and if you live in an area with four-month long dry spells, you might need to fill up your water tank through other means until you get some decent rain again.

Getting Started

Once you’ve got your pipe measurements in and know where your tanks will be placed, the next step is digging a hole. The size of the hole will thoroughly the sort of tanks you’re using, and we’re going to go over the different setups for both greywater and blackwater tanks.

Preparing the Greywater Tank

A greywater tank can be as big as a large capacity IBC Totes container, but we recommend using two 55-gallon water storage barrels for most households.

Once you’re acquired two barrels, you’re going to place them right next to each other; then you’re going to take a PVC pipe that’s about 3 inches wide and shorten it enough that it fits between the two barrels.

Once the pipe can be placed in the gap, you’re going to take a marker, draw a circle where the pipe is supposed to go, and cut a hole in the two barrels there. Then, glue the pipe to both holes and either securely tie the two barrels or glue their sides together so they don’t move or misalign.

Finally, you’re going to use the hole at the top of one of your barrels as an attachment point for the pipes from your house and cut an exit hole near the bottom of your other barrel. After you’ve manually made a new hole, either attach a common tap to it or a simple water stopper so that you can release the water gathered in the barrel whenever you need it. 

Placing the Greywater Tank

Unlike the off-grid septic tank that’s attached to your toilet, the greywater tank doesn’t have to go in the ground and can simply be placed right next to the house. This is because the contents of this tank aren’t as hazardous to require a leach field to filter.

Once you place your greywater tank, connect the pipes to the entry hole that we mentioned, and it’ll automatically start collecting the wastewater from your sink, shower, washing machine, and so on.

Reusing the Water

The runoff that collects from your home will fill up the first tank (called the settling tank) and will start flowing into the second (the surge tank) once the first reaches capacity. The pipe at the top that connects both tanks is a very simple filter that makes sure that the surge tank only collects water while all of the sediment collects at the bottom of the settling tank.

This off-grid homesteading filtering solution works on the basis that the heavier dirt and food particles from your wastewater will be drawn to the bottom of the first barrel and remain there while the second barrel collects the leftover liquid. It’s not exactly as effective as a sewage treatment plant, but it gets the job done.

The groundwater that collects in the surge tank can then be released through the tap that you attached earlier and can be used to either water your flowers or fill your flush tank back up. As we mentioned before, we wouldn’t recommend using this water on any vegetables, but it’s still an effective way to get as much use of the water that would otherwise go to waste.

Preparing the Blackwater Tanks

You’ll need something a bit bigger than barrels for your blackwater container, so we’d recommend getting two large capacity totes containers and modifying them in a similar way to the barrels.

This means making a hole, around 6 inches across near the top of both containers and running a pipe through it. Since these containers will go into the ground, we’d also recommend placing some PVC piping over both of the openings and making a new entry point for the pipes that lead from your house.

You’re going to have these tanks around 6 inches underground, so you’ll need to measure out two PVC pipes that are at least 10 inches long and that have a diameter as large as a basketball. These pipes are going to provide you with access to your septic tank after they go into the ground, so make sure that they’re decently wide.

The new entry point for the pipes is going to need to be placed on top of the settling tank and needs to be level with the pipes from the house. This means that it’s going to be underground if your pipes are also underground, or it’s going to be above ground if your pipes are also above ground.

The High Ground

Most sewage systems carry both liquid and solid waste to the tank by using both the force of the water and the power of gravity. What we mean by this is that as long as your toilet is placed higher than your sewage tanks, even mediocre water pressure should be able to get rid of all of the waste.

Placing the sewage tanks lower than the toilet is easy for houses that are built on a slight incline, but if your property is leveled, you’ll have to dig at an angle to place the tanks lower than the base of your home.

Luckily, you don’t have to dig directly down, and you only need to dig at a 15- or 20-degree angle to give the pipes enough force to carry the water down. The exact measurement is going to depend on how far away the tanks are.

While you want to place your tanks reasonably far from your home just to make sure that there are no unpleasant smells, placing them more than 20 feet away may cause issues. In order to cover that sort of distance, you’ll either need to dig a bit more vertically or make sure that you have a powerful flushing system in your toilet. Otherwise, most of the waste will stick to the pipes and will cause blockage in no time.

A lot of people keep their pipes above ground for ease of access. While we understand this approach, we’d personally recommend putting them under a few inches of soil to ensure that they have a bit more protection against the elements. Plus, removing a bit of soil to gain access to your pipes when there’s a problem isn’t much of a hassle anyway.

Digging a Hole

Once you know the location of your septic tank, start digging a hole that’s a few inches deeper than the containers that you chose to use. After you’ve made the hole deep enough, you’re going to clean out as much of the loose soil as you can.

Most of the soil that’s a few feet below the surface will be too soft and might cause the tanks to shift their position and cause many problems. This is why you’re going to add a layer of the topsoil that you dug up at the bottom of the hole and mix in some cement powder.

Then, tamp down the mixture with a shovel or a more suitable tool that you have at hand to settle it a bit. After about an hour, pour a bit of water and start tamping down the mixture again.

The bottom of the hole needs to be relatively flat, so while you don’t have to use a spirit level, you still might want to stand in the hole and test it out for any hills or valleys that need to be leveled out.

The Drain Field

The drain field, otherwise known as the leach field, is the filter most off-grid septic systems use. This system is essentially two 10-foot long, 5-inch wide perforated pipes connected to the bottom of the surge tank via manually created holes. The pipes are buried underground, and their task is to release the “filtered” liquid waste in the soil.

The waste tank works on a similar concept as the greywater tank: 

  1. Both liquid and solid waste are funneled into the settling tank;
  2. The solid waste remains near the bottom while the liquid waste remains near the top;
  3. The microorganisms and bacteria that form in the tank dissolve the solid waste until it’s little more than sludge and all of the liquids and fats fill-up the settling tank until they start to overflow into the surge tank;
  4. The pipes at the bottom of the surge tank then take in the filtered out liquid waste and disperse it in the soils through the holes in the pipes;
  5. The result is a reduction in ammonia and toxic gas levels in the tank and a tank full of less foul-odored sludge.

While this might not be quite at a level of an industry-grade aerobic digester, this simple system can help make sure that your off-grid cabin isn’t accosted by the horrifying smells that would otherwise come from a septic system that doesn’t have a filter.

Additionally, since you’ll need to schedule an inspection with the EPA to confirm that everything is up to code, any inspector that has a sense of smell will be able to pick up on a septic system that doesn’t have a drain field. While this might not lead to an automatic fine, you might fail the inspection and be forced to reinstall a new off-grid septic system completely.

Putting the Septic Tank Underground

Once the hole is ready, lower the tank and start piling on the dirt. However, before you begin fill-up shoveling, we’d recommend filling the tanks with water first. The empty tanks might start shifting due to the dirt, but the water will add enough weight to keep them in place during the whole process.

If you’ve already attached the drain pipes, then you’re going to start shoveling dirt on top of them evenly. Try to keep them as level and as evenly spaced as possible. Take your time and don’t rush this process, or the dirt might raise the perforated pipes, and the drain field won’t filter out the liquids properly.

After you’ve gotten near the top, attach the septic tank to your house pipes (if you haven’t done that already), and then add the last layer of soil. Tamp it down to make sure that it’s not loose.

Conclusion

a shovel embedder in soil

Off-grid toilets are undeniably one of the bigger pains when it comes to tiny house living. The installation takes ages, all of the parts will cost you quite a bit of money, and any mistake might require you to scrap everything and start all over again.

However, once you set everything up properly, and you’re sure that both the greywater and the blackwater septic systems are working properly, then you’re completely off the grid and you’re ready for just about anything.

Oliver Guess
Oliver is an off-grid living enthusiast currently residing in the mountains of New Mexico. His interests in sustainability originally lead him down the path of an off the grid lifestyle. When he's not tinkering with his broken solar panels, Oliver enjoys searching out hot springs, whittling and cooking.

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